Recently, for example, as a wireless communication technology applicable to an electronic apparatus and the like, Bluetooth® has been known. As a call control profile of the Bluetooth®, a “Hands-Free Profile (HFP)” has been known. The HFP defines a function by which an electronic apparatus such as cell phone controls volume of external device.
When a HFP connection is established between the cell phone and the external device, after an establishment of a lower layer is completed, support function notification is transmitted to the cell phone from the external device. If the external device supports the sound volume control, the support notification includes information representing that the sound volume control is supported. Then, if the HFP connection is established, volume update notification is notified to the cell phone from the external device. According to an initial volume update notification after the HFP connection is established, an initial volume level of the external device is notified to the cell phone from the external device (see FIG. 6). The cell phone receives the support notification of the volume control from the external device and receives the volume update notification (notification of the initial volume level) after the HFP connection is established, so that volume control instruction for the external device is possible. The volume control instruction of the cell phone with respect to the external device represents a function by which the cell phone instructs volume adjustment of the external device. Further, after the volume control instruction of the cell phone with respect to the external device is possible, when volume adjustment based on a volume adjustment operation is performed in the external device, volume update notification is transmitted to the cell phone from the external device.
In addition, according to the HFP, when an incoming call is received in the cell phone, a ringtone called an in-band ringtone can be notified to the external device. According to a function of notifying the in-band ringtone, a voice link is established when the cell phone receives an incoming call, and the cell phone encodes a ringtone and loaded the encoded ringtone on the voice link. The external device receives and decodes the encoded ringtone then plays the decoded ringtone. In general, it is considered that, in relation to the in-band ringtone, ringing volume in the external device can be turned up and down by the volume control instruction from the cell phone. However, when in-band ringtone ringing has not been set, the cell phone notifies the external device of the reception of the incoming call. When the in-band ringtone ringing has not been set, whether the ringtone rings in the external device is dependent on implementation of the external device, but it is usual that a specific ringtone held and generated in the external device is allowed to ring (refer to Bluetooth® Hands-Free Profile 1.5 (Bluetooth® SIG)).
However, such volume control may cause the following problems. First, for example, in the case in which the HFP connection is completely established between external device supporting a volume control function and a cell phone storing the Bluetooth® HFP, when a voice path is established in the cell phone during communication and a speaker of the external device is muted, although a user has performed a volume-up operation to turn up the volume of the cell phone during the communication, the communication volume of the cell phone is not changed and a volume setting value of the muted external device is increased. Thus, when releasing the muting of the external device after the voice path is switched to the external device, voice may ring with a high level.
Second, in the case of a cell phone that performs volume control with respect to external device only when a voice path is not established in the cell phone, and in-band ringtone notification becomes invalid when an incoming call has occurred, the cell phone cannot control the volume of external device. Thus, in such a situation, if the volume cannot be adjusted by the external device, even if volume of a specific ringtone of the external device is too low or high, the volume of the ringtone output from the external device cannot be adjusted.